The present invention relates to an insulation structure for a liquefied gas tank.
In general, a liquefied gas ship for transporting liquefied gas such as LNG at low temperature has a structure as shown in FIG. 1 in which a tank body 1 made of aluminum alloy with its outer surface covered with an insulation layer 4 is supported by heat-insulating supports 2 on a bottom of an inner shell 3 of a hull.
The insulation layer 4 comprises a plurality of insulation panels made of for example polyurethane foam. Each of the panels is supported at its four corners by support members such as rods protruded from the outer surface of the tank body 1 and is fixed to the tank body 1 by tightening a fastening member such as nut on a threaded tip end of each support member through a holding member such as washer.
Fixing the panels at their four corners to the tank body 1 will require a great number of support members, holding members and fastening members, which leads to higher cost as well as much labor and time in mounting the panels, and will cause the panels and the support members themselves to have stresses upon shrinkage of the panels. At joints between the panels, under influence of shrinkage of the tank body 1 which is cooled down by the liquefied gas at low temperature, the adjacent panels apply forces to each other and stress is likely to occur.
In order to eliminate the above problems, the present invention has for its object to provide an insulation structure for a liquefied gas tank in which mounting of the insulation panels is facilitated and occurrence of stresses at joints between the panels is prevented.